(1) Field of the Invention
The present invention relates to a solid-state imaging device.
(2) Description of the Related Art
In recent years, MOS solid-state imaging devices receive more and more attention as imaging devices which take the place of CCD solid-state imaging devices. This is because MOS solid-state imaging devices have many advantages. One of the advantages is that MOS solid-state imaging devices can be manufactured through a CMOS process using existing facilities, and thus stably supplied for the market. Another is that MOS solid-state imaging devices can be increased both in speed and in resolution owing to the capability for providing high-speed readout.
However, since a MOS solid-state imaging device is provided with column amplification circuits which are as many as the number of pixel columns and arranged in the direction of pixel rows, power supplies and ground lines in the MOS solid-state imaging device have an impedance common among all of the column amplification circuits. Because of this, a change in a current in one of the column amplification circuits causes fluctuation in power-supply potential and ground potential, resulting in an effect on all of the column amplification circuits.
Thus, high-intensity incident light on a part of an array of pixels changes a current in the column amplification circuit that amplifies signals from the pixels, and the change in the current affects currents in all of the column amplification circuits. This causes a difference in an output signal between a reset period and an amplification period even from a column amplification circuit that amplifies a signal from a pixel having no incident light. This leads to poor imaging of a white or black streak (generally referred to as streaking) on the sides of a highlight in an output image.
For such poor imaging, Patent Reference 1 discloses a technique for reducing streaking by keeping a current in a column amplification circuit constant using a limiter installed in an outputting unit of a column amplification circuit. The limiter causes a current-source transistor, which is a current source of a source ground amplification circuit, to operate in a saturation region regardless of a signal from a pixel.    [Patent Reference 1] Japanese Unexamined Patent Publication No. 2005-252529